The present invention relates to a vehicle seat, and more particularly, to a vehicle whose seat part is vibrationally movably supported by way of a spring arrangement comprising several springs on a seat subframe, the springs being fastened by means of their respective one end to the seat part and by means of their other end to the seat subframe.
A vehicle bucket seat is shown in DE-PS 1 055 977. The seat part of this vehicle seat is vibrationally movably supported on a seat subframe by way of a spring arrangement comprising several spring elements, such as rubber sliding elements, turn-slide springs or spreading rubber elements. One respective end of the springs is fastened, by the seat part and on their other respective end on the seat subframe. For the longitudinal adjustment of the vehicle seat, the seat subframe is slidably arranged on a frame.
This known vehicle seat has a particular disadvantage in that a buckle of a seat belt anchored on a column can in practice not be fastened on the vibrationally movable vehicle seat itself. On the contrary, in the event of an accident, the risk exists that, because of the belt force acting upon the vehicle seat caused by a vehicle occupant by way of the seat belt and the buckle fastened to the vehicle seat, the spring elements may give or overstretch. If to avoid the problem, the buckle is arranged on the vehicle floor, there is the disadvantage that, when the vehicle seat is longitudinally adjusted, the belt buckle does not follow and the course of the lap belt is not adapted very well to the respective position of the vehicle occupant""s pelvis.
DE-GM 72 39 692 and DE-GM 72 39 693 shows a vehicle seat whose seat part is vertically changeably guided and supported on the seat subframe in each case by way of two parallelogram levers arranged on both sides of the seat. A spring strut, which comprises a spring and a damper, is linked by its upper end to one parallelogram lever respectively on both sides of the seat and is connected by its lower end with the seat subframe. In addition, a hook-type bow is swivellably disposed on the seat subframe so that the spring travel of the seat part can be blocked and this seat part can be fixed on the seat subframe. A handle allows for optional adjustment of the hook-type bow such that, in the event of a stronger compression, a blocking of the seat part takes place or does not take place. The blocking of the seat part takes place only with a time delay after the operating of the handle, when the seat part is compressed sufficiently deeply. In this vehicle seat, an assigned restraining system is not used.
DE 195 07 339 C2 illustrates a vehicle seat whose seat part is resiliently arranged on a seat subframe by way of a tension spring device. By suspending or connecting additional springs, the spring force of the tension spring device can be changed and can be adapted to the weight of the person sitting down in the vehicle seat.
An object of the present invention is to provide a vehicle seat in which the constructive possibilities with respect to designing a restraining system assigned to the vehicle seat are greatly improved.
According to the present invention, this object has been achieved by providing a vehicle seat in which a locking mechanism is operatively arranged between the seat part and the seat subframe such that, in the event of an accident, the seat part is automatically fastened to the seat subframe while vibrational mobility is substantially canceled for an improved effect of a seat belt system assigned to the vehicle seat.
As the result of the seat part which, if required, can be fixed to the seat subframe, for example, the buckle of the seat belt system can be fastened on the seat part without reducing the safety for the vehicle occupant. Particularly in the event of an accident, a vehicle occupant who is strapped to the seat part by way of the seat belt system is therefore also fastened to the seat subframe. Thereby a xe2x80x9cgivexe2x80x9d of the spring arrangement and, for example, a connected raising of the vehicle seat, which are dangerous to the vehicle occupant, can be avoided. Depending on the type of the fixing of the seat part, the swinging mobility can be at least largely eliminated in a manner which lowers the danger of injury to the vehicle occupant.
Another advantage resides in this fixing and of a buckle which can therefore be mounted on the seat part without reducing safety is that is, independently of the longitudinal adjustment of the vehicle seat, the buckle is always situated in the most favorable position relative to the vehicle occupant""s pelvis. In addition, a belt tightener force, which is triggered in the event of an accident, can be introduced into the seat subframe by way of the buckle and the seat part. This triggering occurs without any admission of this force to the spring arrangement and without an at least partial reduction of the effect of a belt tightener. The fastening is advantageous, however not only in the event of an accident. As an alternative, the present invention also contemplates that the vehicle occupant optionally does not fix the seat part for a comfortable driving but for a sporty driving.
Thus, it has been found to be particularly advantageous to use four spiral springs which are preferably arranged laterally in the front and the rear and are supported on the seat subframe. This arrangement results in a particularly advantageous force distribution of the vehicle occupant""s weight on the seat subframe and in a particularly effective spring support.
In a further development of the invention, despite its fixing on the seat subframe, the seat part is longitudinally adjustably fastened on the vehicle floor. As a result, the vehicle occupant is provided with a significant adjusting possibility.
It has also been found to be advantageous to use approximately C-shaped spiral springs which have very good suspension characteristics and, in addition, hardly permit any vibrations of the seat part in the horizontal direction. With approximately crescent-shaped spiral springs, it has been found to be particularly advantageous to use an elastically flexible core which is particularly suitable for damping vibrations.
By receiving the two ends of the spiral springs of one clamp-type socket respectively, a particularly stable connection is established between the respective spiral spring and the seat part or the seat subframe. In addition, it has been found to be advantageous to produce the core from a plastic material of a high damping characteristic. The core can be made, for example, of a polymer or an elastomer, depending on the comfort required for the vehicle occupant.
An approximately U-shaped frame connected with the spiral springs makes the vibration movement of the spiral springs is made uniform, particularly for increasing comfort and safety.
In a particularly simple manner, the seat part can be fixed on the seat subframe by a locking mechanism which is provided between the seat part and the seat subframe and can be operated by an accident-caused belt tension force of the seat belt.
Finally, the locking mechanism is particularly effective when comprised of at least two toothed racks assigned to one of the rearward spiral springs respectively. One of the toothed racks respectively is preferably, by a belt tension force, on the buckle, on one hand, and, on a fitting, on the other hand, which fitting is fastened on the seat part for fixing one end of the seat belt on the side facing away from the belt buckle, engaged with corresponding locking devices on the seat part. Of course, it is also within the scope of the present invention that a toothed rack for locking the seat part with the seat subframe is provided on each spiral spring.